The effect of two-step surface modification for Ti-Ta-Mo-Zr alloys on bone regeneration: An evaluation using calvarial defect on rat model

This study was conducted to explore the optimal anodization conditions and to evaluate the bioactivity of the coated-CaP TiO2 nanotube layer on new Ti-Ta-Mo-Zr alloys. The nanotube was fabricated by anodization process, then anodized samples were treated with cyclic precalcification. Critical agents for nanotube morphology are anodizing voltage, time, and electrolyte compositions. The surface features were analyzed by field emission scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer; X-ray diffractometer and surface roughness tester. The results showed clearer morphology and higher density of the nanotube structure on the surface of 71Ti-20Ta-1Mo-8Zr alloy than that of other alloys. The presence of precursors of hydroxyapatite (TCP, OCP) on the precalcified surface of this alloy inclined a high potential of hydroxyapatite formation. For in vivo test, membranes treated with either anodization (AH) or precalcification-combined anodization (APH) were covered on rat calvarial defects (8 mm of diameter) for 5 weeks, and untreated membranes were used as the control. The newly formed bone was evaluated by microcomputed tomography, histologic and fluorescent analysis. The newly formed bone on the APH membrane showed higher bone mineral density and a contact osseointegration, indicating that the APH treatment promotes durable osteogenesis at the early stage of bone defect repair.